Liquid crystal displays (LCD's) used in televisions, computers, and other video display devices produce predetermined images and control light transmission to produce video displays. LCD's are particularly suited for flat panel displays because of their superiority in resolution, color image display and image quality. LCD's do not emit light themselves and therefore utilize backlight devices behind the LCD panel to produce a visible video display. Cold cathode fluorescent lamps (CCFL's) have been used for various illumination purposes and are particularly suited for use as a backlight apparatus in conjunction with liquid crystal displays such as TFT-LCD's (thin film transistor-liquid crystal displays) in televisions, computers, and other video display technologies. The performance and quality of the video display is optimized when the illumination is sufficient and uniform throughout the display. Non-uniform illumination degrades the quality of the displayed image. Technological advances in the video display industry enable the reliable production of increasingly large video displays and as video display devices become larger, it becomes increasingly more challenging and important to provide a uniformly illuminated display device.
LCD panels used in televisions and other video display devices, typically utilize a CCFL backlight apparatus that consists of a housing that contains numerous elongated tubes of cold cathode fluorescent lamps and includes reflective internal surfaces. The housing typically includes a generally flat, reflective back portion and an open face that faces the LCD, but the housing is generally separated from the LCD by several layers of material that condition the light as it travels from the CCFL backlight apparatus to the liquid crystal display. For example, a diffuser plate and one or more multilevel diffusers may be present between the backlight apparatus and the liquid crystal display. Additionally, one or more prism sheets may be included between the diffusers if more than one diffuser is used. A deformation of the diffuser plate, the diffusers, or the prism sheets can result in non-uniform illumination provided to the LCD array and therefore an video image of inferior quality is seen by the viewer. When the CCFL backlight apparatus is of considerable size and a correspondingly sized diffuser plate is disposed against or in close proximity to the open face of the backlight apparatus housing, a common problem is for the diffuser plate to sag or deform so that it is not level with respect to the backlight apparatus. This produces an undesirable non-uniformity of illumination.
It would therefore be desirable to provide a backlight apparatus that delivers uniform illumination to a display device regardless of the size of the display device. In particular, it would be desirable to support the diffuser plate at a level orientation with respect to the backlight device.